1. Field of the Invention
The present invention relates to the replacement and repair of fluid supply service pipes, in particular, the invention relates to the insertion of a replacement pipe into an existing, live gas service pipe, without the necessity of excavation. The invention is also related to the testing and sealing of the newly established pipe before the new pipe is put into service.
2. Description of Related Art
In the past, replacement of underground fluid service pipes, particularly gas service pipes, involved excavation of areas adjacent the affected pipe, and temporary termination of the flow of gas at a point upstream of the interface of the new pipe with the old pipe. Improvements in this technique have been proposed, whereby the new pipe is inserted into the old pipe, without the need for excavation. However, the prior art fails to solve problems associated with internal sealing of the pipe, testing procedures, and seal removal. In particular, prior art systems fail to adequately address the problem of ensuring that a permanent fluid tight seal is effected between the ends of the newly installed pipe and the volume between the new pipe and the old pipe. Blind methods, where sealant is installed without the ability to visually confirm complete filling of the void between old and new pipes, suffer from the possibility of gaps in the sealant which would provide a path for gas to travel from a point at the interface of the old pipe and the terminal ends of the new pipe into the void between the old and new pipes, resulting in a failure of the repair of the old pipe. Air entrapment also leads to gaps in the sealant. Prior art systems also fail to adequately address the need for pressure testing of the repaired section before that section is placed into service, as dictated by DOT .sctn.49 part 192 and other guidelines. Prior art systems also suffer from the possibility of unwanted movement of the ruptured or discarded temporary plug, because the plug is not completely controlled after it has been removed from its original position during the temporary sealing stage. This may result in movement of the discarded plug into the new flow path of the fluid, partially or completely blocking the flow of fluid. Also, prior art systems have failed to provide for economical and reliable elements which may be utilized in a cost efficient manner, thereby reducing the practical benefit over traditional methods of pipe replacement.
These and other problems are addressed and solved by the present invention.